Navien error code E110 indicates an overheating issue in your tankless water heater or boiler, requiring you to safely inspect venting and water flow.
Table of Contents
- What does error code E110 mean on a Navien unit?
- What usually causes a Navien E110 overheating fault?
- What are the quick fixes to try first?
- What should you do if the initial fixes fail?
- Which fix matches your specific E110 symptom?
- When should you stop troubleshooting and call a professional?
- What details should you prepare before calling a technician?
- How can you keep error code E110 from returning?
What does error code E110 mean on a Navien unit?
Navien error code E110 indicates that the appliance has registered an overheating condition inside the unit.
When internal temperatures exceed safe operating limits, the safety sensors trigger the Navien error code E110 to protect the heat exchanger from severe damage. This fault can appear on various Navien tankless water heater and combi-boiler models when airflow or water circulation is restricted.
- The internal safety sensor has detected an excessive temperature reading.
- Your Navien unit halts operation immediately to prevent permanent hardware damage.
- Blocked exhaust or intake pipes can trap high heat inside the appliance.
- Insufficient water flow through the heat exchanger causes rapid internal overheating.
- A malfunctioning temperature sensor might send false overheating alerts to the control board.
What usually causes a Navien E110 overheating fault?
Common causes include blocked intake or exhaust venting, restricted water flow, scale buildup, or a faulty sensor.
Pinpointing the root cause of Navien error code E110 starts with checking external obstructions and internal fluid movement. Debris in the venting system or mineral scale inside the heat exchanger frequently restricts normal operations and triggers safety shutdowns.
- Leaves, nests, or ice blocking the outdoor concentric vent termination cap.
- Heavy mineral scale accumulation restricting water circulation inside the heat exchanger.
- A partially closed cold water supply valve reducing the necessary flow rate.
- A defective high-limit temperature switch or thermistor providing inaccurate readings.
- Internal circulation pump failure on combi-boiler models causing stagnant hot water.
What are the quick fixes to try first?
Perform a power reset, check water valves, and inspect accessible intake and exhaust vent pipes.
Before attempting any inspection, turn off the power switch or breaker to protect yourself from high-voltage components. Clear any obvious debris from the exterior vent terminals and verify that all water supply valves are fully open.
- Turn off the power switch on the front of the unit or flip the dedicated circuit breaker.
- Locate the outdoor intake and exhaust vent terminals and clear away any leaves, dirt, or snow.
- Verify that the cold water supply valve and gas shutoff valve are opened to the maximum position.
- Wait five full minutes to allow the internal components and sensors to cool down completely.
- Turn the power switch back on and check if the Navien error code E110 clears from the display.
What should you do if the initial fixes fail?
Inspect water filters for debris, check pump operation, and look for internal blockages.
If the Navien error code E110 persists after a reset, you must examine internal components for restrictions. Turn off the power and water supply before removing the front cover to check the internal inlet water filter for trapped sediment or scale.
- Turn off the power breaker and close the cold water supply valve before opening the cabinet.
- Place a small towel underneath the unit and unscrew the cold water inlet filter plug.
- Pull out the mesh water filter and rinse away any accumulated debris or mineral flakes under running water.
- Reinsert the clean filter securely and tighten the plug to prevent leaks before turning the water back on.
- Power the unit back up to test if proper water flow resolves the E110 fault code.
Which fix matches your specific E110 symptom?
Match your appliance behavior with the corresponding cause and recommended action in this reference table.
Different operational environments can trigger Navien error code E110 with unique secondary symptoms. Use this table to identify your exact scenario and apply the correct targeted solution.
| Symptom | Likely cause / fix |
|---|---|
| Code appears during heavy hot water use | Scale buildup; flush heat exchanger with vinegar. |
| Code appears immediately upon startup | Faulty temperature sensor; test and replace sensor. |
| Rattling noise inside unit with E110 | Blocked vent pipe; clear exhaust and intake lines. |
| Low water pressure accompanied by E110 | Clogged inlet filter; remove and clean mesh filter. |
When should you stop troubleshooting and call a professional?
Stop immediately and call a technician if you smell gas, suspect a sealed-system failure, or need component replacements.
Gas appliances require strict safety adherence to prevent carbon monoxide leaks or explosions. If basic resets and filter cleanings do not clear the Navien error code E110, professional diagnosis with specialized tools is required.
- Stop and call a licensed professional immediately if you detect any smell of gas near the appliance.
- Contact a technician if troubleshooting requires touching gas valves, gas piping, or combustion chambers.
- Call for service if the high-limit switch or main control board needs testing or replacement.
- Reach out to an expert if frozen outdoor venting caused structural damage to the exhaust system.
- Consult a certified plumber if chronic scale buildup requires a professional descaling pump flush.
What details should you prepare before calling a technician?
Gather your exact model number, serial number, installation date, and a history of tried troubleshooting steps.
Having accurate information ready speeds up warranty claims and helps service technicians bring the right replacement parts. Locate your rating plate on the side of the cabinet to find the full product details.
- Write down the exact alphanumeric model number and serial number from the side cabinet label.
- Note the approximate date of installation and whether the appliance is still covered under manufacturer warranty.
- Prepare a clear summary of all troubleshooting steps you already tried, including power resets and filter cleanings.
- Record any other error codes that flashed on the digital display alongside the main E110 fault.
- Keep your local gas utility or preferred certified plumbing contractor contact information accessible.
How can you keep error code E110 from returning?
Perform annual maintenance, clean inlet filters regularly, and protect outdoor venting from seasonal blockages.
Preventative care ensures your Navien system operates efficiently without unexpected thermal shutdowns. Regular upkeep stops mineral deposits and debris from choking the critical airflow and water pathways.
- Schedule an annual professional maintenance service to flush the heat exchanger and check combustion levels.
- Inspect and clean the cold water inlet filter every six months, especially in areas with hard water.
- Check your outdoor intake and exhaust vent terminals monthly for spider webs, leaves, or winter snow buildup.
- Monitor your home water pressure to ensure it stays within the recommended limits specified in your manual.
- Test the pressure relief valve periodically to guarantee safe operation and proper internal pressure release.
Frequently Asked Questions
Can I use my Navien unit if error code E110 keeps resetting itself intermittently?
You should not ignore intermittent E110 codes even if the unit starts working again after a power reset. Repeated overheating events indicate an underlying restriction in airflow or water circulation that can permanently damage the internal heat exchanger if left unresolved.
Does Navien error code E110 mean my heat exchanger is completely broken?
Not necessarily, as E110 usually points to external factors like blocked venting, scale accumulation, or a faulty sensor rather than a cracked heat exchanger. However, running the appliance repeatedly under high-heat conditions without fixing the root cause can eventually lead to permanent hardware failure.
How often should I flush my Navien water heater to prevent overheating errors?
You should flush your Navien tankless water heater or boiler at least once a year with food-grade white vinegar. If your home has very hard water with high mineral content, you may need to perform this descaling procedure every six months to prevent severe scale buildup.
What should I do if the E110 error code appears immediately after a new installation?
If E110 appears on a newly installed unit, contact your installing contractor right away to verify proper setup. Common installation errors causing this include closed service valves, incorrect gas pressure settings, or restricted venting configurations that violate manufacturer guidelines.
Is error code E110 covered under the Navien manufacturer warranty?
Warranty coverage for Navien error code E110 depends on the specific failed component and whether the unit was registered and installed by a licensed professional. Check your owner manual or contact manufacturer support with your serial number to confirm exact warranty terms for parts and labor.
Bottom Line
Turn off the power breaker immediately and inspect your outdoor vent terminals for blockages as the first troubleshooting step.
Sources
- Navien user manual
- Navien installation manual
- manufacturer support page